At home we have 10G internet, but our router only has an RJ45 out. To connect it to our switches, we need to use an RJ45 SFP+ module. Some of you might know that these get ridiculously hot (90°C at times). So hot in fact that it sometimes shut down. Leaving the door open for ventilation helped a bit (85°C), but didn’t make my wife happy, so I had to come up with another solution.

I connected an old Noctua PC fan to an unused 12V power supply with a 2€ controller from aliExpress.

I also stuck mini heatsinks (meant for RaspberryPi) directly to the SFP+ module.

Now the temperatures are <75°C, and my wife and I are both happy.